1. Technical Field
The present invention relates in general to high density electronic packaging which permits optimization of the number of circuit elements to be included in a given volume. More particular, the present invention relates to a method for fabricating a three-dimensional multichip package having a densely stacked array of semiconductor chips interconnected at least partially by means of a plurality of metallized trenches in the semiconductor chips.
2. Description of the Prior Art
Since the development of integrated circuit technology, computers and computer storage devices have been made from wafers of semiconductor material comprising a plurality of integrated circuits. After a wafer is made, the circuits are typically separated from each other by dicing the wafer into small chips. Thereafter, the chips are bonded to carriers of various types, interconnected by wires and packaged. Along with being time consuming, costly and unreliable, the process of physically attaching wires to interconnect chips often produces undesirable signal delays, especially as the frequency of device operation increases.
As an improvement over this traditional technology, stack or packages of multiple semiconductor chips have become popular, e.g., reference U.S. Pat. No. 4,525,921, entitled "High-Density Electronic Processing Package - Structure and Fabrication." FIG. 1 depicts a typical semiconductor chip stack, generally denoted 10, consisting of multiple integrated circuit chips 12 which are adhesively secured together. A metallization pattern 14 is provided on one or more sides of stack 10 for chip interconnections and for electrical connection to circuitry external to the stack. Metallization pattern 14 includes both individual contacts 16 and bussed contacts 18. Stack 10, with metallization 14 thereon, is positioned on the upper surface 21 of a substrate 20 which has its own metallization pattern 22 thereon. Although superior to the more conventional technique of individually placing chips on a board, substrate or multichip carrier, both in terms of reliability and circuit performance, this multichip stack approach is still susceptible to improvement in terms of density and reduction in the length of chip wiring. Obviously, any improvements in such package characteristics will produce a lower cost, lower power higher density, reliability and thereby providing better performing device.